Experimental Study on the Variation of Optical Imaging Characteristics with Zenith Angle due to Internal Solitary Waves in Sunglint

Internal solitary waves (ISWs) change the roughness of the sea surface, thus producing dark and bright bands in optical images. However, reasons for changes in imaging characteristics with the solar zenith angle remain unclear. In this paper, the optical imaging pattern of ISWs in sunglint under different zenith angles of the light source is investigated by collecting optical images of ISWs through physical simulation. The experiment involves setting 10 zenith angles of the light source, which are divided into area a the optical images of ISWs in the three areas show dark-bright mode, single bright band, and bright-dark mode, which are consistent with those observed by optical remote sensing. In addition, this study analyzed the percentage of the dark and bright areas of the bands and the change in the relative gray difference and found changes in both areas under different zenith angles of the light source. The MODIS and ASAR images display a similar brightness-darkness distance of the same ISWs. Therefore, the relationship between the brightness-darkness distance and the characteristic half-width of ISWs is determined in accordance with the eKdV theory and the imaging mechanism of ISWs of the SAR image. Overall, the relationship between them in the experiment is almost consistent with the theoretical result.